The invention relates to surface treatment of panel-, plate- or sheet-like blanks which are made of a metallic, plastic and/or other material. More particularly, the invention relates to improvements in methods of mechanically surface beneficiating panel-, sheet- or plate-like blanks (hereinafter called blanks for short) and to panel-, plate- or sheet-like bodies which constitute the treated or converted blanks.
It is often necessary to provide a panel-, plate- or sheet-like body with one or more layers of paint, lacquer and/or other material. Such layers are applied to enhance the appearance of the body and/or to reduce the likelihood of corrosion. It is also known to artificially or intentionally oxidize the surfaces of panel-, plate- or sheet-like bodies, especially of bodies which consist of or contain aluminum. Still further, it is known to bond or plate one side or surface of a first panel-, plate- or sheet-like body to one side of a second panel-, plate- or sheet-like body in order to protect the first and/or the second body from corrosion and/or other undesirable influences or to enhance the appearance, strength and/or other desirable characteristics of the first and/or second body.
The sides or surfaces of a panel-, plate- or sheet-like blank, particularly a rolled metallic blank, are often coated with films of grease or other lubricating material which is applied by rolls or by other component parts of rolling mills or other machines or production lines wherein the blank is made or treated. Such films interfere with predictable application of layers of lacquer, paint and/or other coating materials. Moreover, the films often interfere with predictable artificial oxidation of one or both sides or surfaces of a rolled blank, either in air or in a vessel wherein the blank is caused to react with an oxidation-promoting liquid substance.
Attempts to remove the films of grease and/or other lubricants include a preliminary treatment of blanks with suitable solvents. A drawback of such procedure is that the preliminary treatment of blanks takes up a substantial amount of time. In addition, care must be taken to gather all volatile ingredients of the solvent as well as to dispose of the removed lubricant in an ecologically acceptable manner.
It was already proposed to enhance the ability of exposed surfaces of metallic, plastic and/or other blanks to reliably retain layers of lacquer, paint or the like by sandblasting and/or by an analogous treatment, e.g., with minute particles of glass or metal (such as steel). Sandblasting or an analogous treatment can accomplish two objects, namely that of removing the film of lubricant as well as that of roughening the treated surface or surfaces to ensure more predictable and stronger adherence to layers of paint or the like. As a rule, sandblasting or a similar treatment is resorted to in connection with the surface treatment of metallic sheets having a thickness of up to 2 mm. However, it has been found that intensive sandblasting or a similar treatment (such as is necessary to reliably remove the film or films of lubricant and to adequately roughen the treated surface or surfaces) often results in undesirable localized densification of the material of the treated blank. Such densification causes buckling and/or other deformations as well as undesirable hardening of densified portions of the material of the thus treated blank. This is often undesirable or plain unacceptable, either because it affects the appearance of the treated body and/or because it entails unpredictable changes of characteristics such as can prevent further treatment of the body in a desired manner. For example, a sheet which has been treated by sandblasting or was subjected to an analogous treatment is likely to develop cracks as a result of subsequent folding, bevelling, canting or other profiling.
In accordance with another prior proposal, films of lubricant are removed by subjecting the surface or surfaces of blanks to the action of rotary brushes or grinding tools. The brushes or grinding tools roughen the surfaces of the blanks to render them more receptive for layers of lacquer or the like. It has been found that such treatment can greatly enhance the ability of the surfaces of metallic panels, sheets or plates to accept and retain layers or coats of paint or the like as well as to undergo predictable artificial oxidation, either in the atmosphere or as a result of contact with a liquid oxidant in a vessel or the like. However, the just discussed treatment also brings about certain drawbacks which reduce its utility and applicability. Thus, and if the grinding or brushing operation does not result in a densification of the outermost stratum or strata of a thin panel, sheet or plate of metallic material (i.e., if the grinding or brushing operation is intentionally carried out with a view to avoid localized densification and hence the likelihood of cracking as a result of flexing, bevelling or an analogous deforming operation), the thin panel, sheet or plate is not likely to retain a layer of lacquer, paint or oxide if such sheet or plate is shaped (e.g., bent, bevelled or similarly treated) subsequent to application of the layer of lacquer or the like. The layer is likely to become separated from the brushed or ground surface of the panel, sheet or plate in the region of each bend or fold, and such separation affects its appearance, its useful life and/or other desirable characteristics.
U.S. Pat. No. 2,907,151 to Peterson discloses a method of conditioning metal strips, sheets and the like. The patented method includes cleaning the surface or surfaces of a metallic strip with rotary brushes, spreading an abrasive component into the region of contact between the strip and the brushes, and thereupon arcuately flexing the surface-roughened strip. The patentee also proposes to stretch the material of the strip prior to brushing. Such treatment is not acceptable for a number of applications and contributes significantly to the cost of the ultimate product. The surface of the strip normally undergoes pronounced densification as a result of treatment by the stretching rollers which are caused to apply pronounced pressure.
U.S. Pat. No. 3,082,517 to Holowaty proposes to spray abrasive material between two overlapping sheets one of which is coated with an adhesive material, and to thereupon apply pressure in order to embed the abrasive particles in the adjacent surfaces of the two strips.
British Pat. No. 495,421 to Daniels discloses a surface treatment which involves brushing or etching of metallic sheets or rolling of metallic sheets between specially prepared surfaces of rolls. The metallic blanks which are treated in accordance with the teaching of Daniels are smooth-surfaced soft sheets of aluminum or aluminum alloy. The sheets are debossed by pressing against their surfaces a perforated, woven or mesh-like metallic or textile material in sheet form. A drawback of the patented method is that one cannot avoid undesirable hardening of certain portions of the material along the treated surfaces.
U.S. Pat. No. 2,335,196 to Pecsok discloses a method of removing scale from metal sheets. The method includes spraying a hot sheet which issues from the mill with water, passing the sheet through breaker rolls to break the scale into particles, flexing the sheet over a roll to raise the edges of the particles of scale, and brushing off the scale.
Applicant is further aware of the disclosure in French Pat. No. 2,252,175 to Vsesojuzny Nauchnoissledovatelsky Institut, and of the article by W. K., Erickson entitled "Metal cleaning by microscalping" (Iron and Steel Engineer, Volume 54, No. 2, February 1977, pages 43-46).